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strantor

Setting up braking with a drive

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I have a spool on a shaft that is attached to a motor. The spool is paying off wire, through a dancer, to elsewhere, where it is being pulled at a more or less constant rate, with frequent starts & stops. The motor is controlled by a yaskawa V7 drive with PID input from the dancer. I want to add braking to the setup. I don't want regenerative braking, braking resistors, or DC injection. I want to use a separate air brake. What needs to happen is the drive needs to control an I/P transducer or proportional valve to regulate air to the brake. If the dancer is going down a little too fast, a little air needs to be applied to slow the spool down. If the dancer is plummeting down, air needs to be applied pull pressure to bring the spool to a stop. If the dancer is on the rise or maintaining position then I want no air applied. Basically, whatever the drive would normally do to stop the spool, I need it to instead apply air. I though about assigning a multifunction analog output as "inverse PID" and controlling an I/P transducer or proportional valve from that, but the Yaskawa V7 cannot assign PID monitors to an output. I started looking at the online manual for the Yaskawa A1000 drive and among all it's features I can't seem to find a way to assign the inverse of PID to an output. As I interpret the manual, you can assign PID output to an analog out, & you can have inverted PID, but you can't have the drive operating the motor in "normal PID" and assign "inverted PID" to an output. It seems to me that this should be a pretty common application, so I must be missing something. So, my question to you all is, "How would you go about setting up an air brake with PID?" Am I barking up the wrong tree? What drive should I be looking at? Thanks, Charlie

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How about inverting the Dancer Position and Reference so the PID is inverted?

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You mean physically reverse the wires from the dancer to the PID input of the drive? That's what I'm already doing (via a relay) when I want to reverse - it inverts the PID. That's not really what I'm trying to accomplish here, as I want the PID to the motor stay the same, with an additional output (0-10V or 4-20mA or other) which is the opposite of pid output (not PID setpoint). Maybe I can explain better what I want by comparing it to a heater PID controller. Many heater controllers have 2 outputs - a heating output and a cooling output. the cooling output comes on the PID overshoots, or when you turn the temp down, or for any reason your temp goes too high. So, I want my motor functioning the same, but I want the braking to come on if PID overshoots, speed goes higher than desired, or I turn the speed down. All that is, unless I misinterpreted what you were saying.

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Have you reasearched Yaskawas internal programming software on the drive. Depending on the model you may have you can input 50 or 100 steps of what is basically function block control. Of course you need the software and to get that you have to go to a three day training in Chicago.... Either way internally you can use these function blocks to create exactly what you are asking for, you can even change a parameter based on a set of inputs.........

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I had no Idea about that, thanks! Is it a seperate software than the drivewizard software that they include on a disk when you order the drive? where can I get info on that class?

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